The mechanisms of transcription initiation and transcription termination and their regulation will be studied in bacteriophage lambda. The studies of transcription initiation will concentrate on the right operator-promoter complex of lambda. This DNA region contains two promoters and multiple repressor binding sites which direct transcription both to the right and to the left from this region. Products of two lambda genes, cI and cro regulate the initiations of these transcripts. This project will study the structure of this region by isolating mutations affecting this region and analyzing them with nucleotide sequencing, physiological, and genetic techniques. The studies of transcription termination will concentrate on tR1, one of the termination sties for transcription orginating at the right operator-promoter complex. Termination at this site is regulated by the host-encoded p termination protein and by the phage encoded N anti-termination protein. Mutations affecting termination at tR1 will be isolated and analyzed with the techniques used to study the operator-promoter complex. Mutations in the two control sites will be isolated and mapped with a set of deletion mutations, also to be isolated. The nucleotide changes in the mutations will be determined by the DNA sequencing techniques developed by Maxam and Gilbert. The physiological alterations of these mutants will be compared with their nucleotide changes to determine the role of the individual sequences within the two control sites. The results will be used to develop models for the regulation of bi-directional transcription, transcription termination, and protein-nucleic acid interaction. They will also allow an assessment of the physiological role of transcription termination in the growth and development of the phage.